The submarines would supplement China's existing fleet of about 65 subsurface vessels, including indigenously built nuclear and ballistic missile submarines.

China has also produced several of its own variants of Russia's Sukhoi Su-27, Su-30 and Su-33 warplanes and is in the process of developing its own stealth fighters. The BBC quotes China's People's Daily as saying the advanced Su-35s from Russia would "effectively reduce pressure on China's air defense" as China moved ahead with its stealth planes.

Last year, IHS Jane's, quoting the Moscow daily Kommersant, reported that Moscow was leery of a deal with China because it was afraid Beijing would illegally copy the weapons.

Kommersant said:

"[Moscow] is requiring that Beijing provide a legally binding guarantee that it will refrain from making reverse-engineered copies of the Russian fighter — largely so that this does not create a potential competitor in the market to sell the aircraft to other countries. China is [in] no hurry to provide this guarantee."

The reports come as Beijing and Moscow have moved closer in an apparent desire to counterbalance U.S. interests in Asia and Europe and The China Daily described Xi's visit to Russia as a "well-deserved riposte to Washington for America's military 'pivot' to Asia. Xi is executing China's own 'pivot' — the visit to Moscow to cement ties with" Russian President Vladimir Putin, according to the BBC.